Extraction of montan wax



Feb. 2i, 1933.

Filed March l5, 1928 E. ROECKNER ET AL EXTRACTION 0F MONTAN WAX ra 714/5045 W459i@ Inven ions Patented Feb. 21, 1933 ERICH 'ROECKNER, OF HALLE-ONTHESAALE, AND FRITZ ZSCHOGII, 0F UNTERROB- LL'NGEN, GERIAN'Y, .VASSGNORS TO A. RIEEECKSCHE IfONTANVEB/KE A''EN- GESELLSCHAFT, OF HALLE-ON-THE-SAALE, GERMANY EXTRAGTION GF MONTI-LN WAX Application filed March 13, 1928, Serial No. 261,329, and in Germany April 4, 1927.

This invention relates to the extraction of Montan wax from brown coal. TWhen extracting Montan wax from brown coal in the u manner which was hitherto usual in Geri many, for instance,` the previously dried brown coal was extracted with low boiling solvents or mixtures of solvents, substantially at atmospheric pressure. The temperature of the solvent had to be kept in this case so low that no marked hyper-pressure was formed in the apparatus. This process is carried out in the following manner.

The previously dried coal is introduced into vertical extracting chambers, each chamber consisting of a cylindrical or coneshaped vessel provided with tight-closing covers at the top and at the bottom. At the top of each chamber a lateral inlet pipe for the solvent is provided and at the bottom a lateral outlet pipe forming a siphcn for withdrawing the solvent enriched with Montan wax. The said chambers are laterally either separately or as a plurality surrounded by ajacket,the intervening space between the jacket and the chambers servingfor receiving the steam by which the chambers are heated.

For filling the chambers with coal the upper covers are lifted. After the chambers are charged with coal, the covers are again tightened and the solvent or mixture of solvents is introduced from a reservoir. When the chambers are filled with the solvent, the latter flows through the outlet pipe into an evaporator heated by means of steam coils and is there evaporated, the extracted wax being left as aresidue. The solvent vapors pass through a pipe leading from the evaporator to the jackets of the extracting chambers laterally into the `lower part of the intervening space between the extracting chambers and the jacket, flowing around the chambers and transferring a part of theirheat to'them. The cooled vapor then leaves the heating jacket through a further lateral pipe at the top and passes to one or more coolers in which the solvent is condensed. If the solvent vapor produced in the evaporator is not entirely required for heating the chambers, y part of it may also be led directly to the coolers through a branch pipe. As the solvent ilowing through the wet coal to be extracted has absorbed water, which is evaporated too in the evaporator, the condensate obtained in the coolers consists of two liquids insoluble in each other, viz a solvent insoluble in water on one hand and water or water mixed with that part of the solvents which are soluble in water on the other hand. rlhese two liquids are separated in a liquid-separator' and from the aqueous layer the water-soluble component of the solvent is recovered in a concentrated condition, if required, by rectication. The solvent or mixture of solvents thus regenerated is again introduced into the circle, as above described.

After the coal is suiiiciently extracted, the supply of solvent to the extraction chambers is cut oil, and life steam is introduced through the bottom of the chambers to freev the coal from the adhering solvent. ln the same lmanner the Montan wax obtained as a residue in the evaporators is freed from the remainders of solvent by live steam. The resulting mixture of steam and solvent vapors is conducted to the coolers, as above described, where they are condensed and then separated in separators. The extracted and steamed coal is removed from the extractors by opening the bottom cover. lt falls down into a receiver and is carried away.

The here described method of extracting Montali wax from brown coal at atmospheric pressure, as it was hitherto used, involves manifold inconveniences. F or instance, when the extraction has to be carried out at elevated temperatures, solvents of relatively high boiling point can only be employed. Such solvents, however, are removed from the extracted coal and likewise from the extract with difliculty and with considerable consumption of heat, with the result that the cost is increased and a great loss of solvents is entailed. @n the contrary, when using solvents of lower boiling point such as benzene, one is restricted to working at relatively low temperatures. As Montan kwax is only slightly soluble in low-boiling solvents at ordinary temperature, the extraction requires a relatively long time and a considerable consumption of solvents, if a com lete separation of the soluble wax from t e coal is desired. Therefore the extraction is preferably interrupted before the last part of bitumen is dissolved, whereby, of course, the output of Montan wax is decreased.

Now we have found that all these inconveniences are wholly or almost wholly eliminated by carrying out the extraction from the coal (either in its moist state as it comes from the pit or preliminary dried) in a closed apparatus under a pressure slightly exceeding the atmospheric pressure, produced by correspondingly elevating the temperature of the solvent. The exact degree of temperature and therewith the pressure 20 depends upon the nature of the solvent used.

We are aware that it has already been proposed to extract waxlike substances from brown coal with solvents in a closed vessel under pressures between 10 and 60 atmospheres and at temperatures of from 150 to 250 C. However for this process expensive high-pressure apparatus are required and the product of extraction has quite another composition than commercial Montan wax.

One of the advantages attained by our improved method is that at the elevated temperature the solubility of the Montan wax and likewise the extracting rate are greatly increased whereby the production is augmented to a considerable extent. Moreover during the same space of time the Montan wax is extracted from the coal to a far greater extent than when working without over-pressure. By extracting with benzene, according to the method hitherto adopted, the extracted coal still contains 3.5% of bitumen soluble in hot benzene, whereas this residue is reduced to 0.5% when extracting the coal with benzene at about 90 C., that is to say, at an overpressure of about 0.5 atm. without increasing the time of extraction. Calculated upon the extract, this corresponds to a surplus output of about 20 to 25%. i

When extra ting under slight over-pressure, solvents of lower boiling-point may be used without any risk. Such solvents are furthermore distinguished by being more easily and more completely expelled from the extract and especially from the extracted coal. Hereby the losses of solvents as well as the consumption of steam are substantially reduced. In our present process the consumption of heat is smaller than when employing the method hitherto adopted. This is partly due to the fact that the quantity of heat, transmitted, in our process, to he solvent before the extraction, brings about the above described advantages, and

is better utilized than the heat needed, when extracting at ordinary pressure and at a low temperature, for distilling olf the solvent from the extract and for desiccating the extracted coal.

Our improved method may be carried out in the apparatus hitherto used for continuous extraction at ordinary pressure. It is onl necessary to use a receiver provided, for instance, with an automatic double-seated. valve actuated by a float instead of the liquid separators of usual type employed for separating the recovered condensates of water and solvent. Besides this a safety pressure controlling device of usual construction is to be inserted into the ap aratus.

In the annexed drawing we have illustrated by way of example a plant for carrying out our improved process. a and a are identical separating receivers under ressure, b and b being valves actuated by oats c, c respectively. d is an air separating cooler, and e a safety pressure regulator. The way of the fluids is indicated by arrows.

An air outlet conduit, coming from the extractors (of well-known construction) and subjected to the overpressure in the extractors, enters the system at f. The su plied vapors of water and solvent are con ensed in the air separator d. The condensate passes through pipe g to the separator a where the condensate insoluble in water, as benzene, is separated from its aqueous ortion as, for instance, diluted alcohol. he former flows off by pipe h into a collecting vessel (not shown) whence it is returned to the extractors. The latter is withdrawn through pipe i into a rectifyer; the rectified liquid is again added to the benzene.

A pipe k communicates with the separator a to carry the air with the not yet condensed solvent vapors to a safety pressure regulator e which opens under excessive pressure. The eseapin air is introduced into a washing device not shown) where the last remnants of solvent are separated. Another pipe Z forming the air separating conduit of the liquid separators of usual type (not shown) communicates at f with the conduit coming from the extractors. These liquid se arators of usual type serve, in the usual limts, to separate the solvent distilled o from the extracted Montan wax or expelled by steam and condensed. Into conduit Z a further separator under pressure a may be inserted similar to a for collecting and separating the vapors meanwhile condensed. Pipes h and i are for withdrawing the nonaqueous and the aqueous portion respective.

yIt will of course be understood that our invention is not conned to the use of the apparatus shown, by way of example, in the drawing, but our invention nerally comprises separating the condense solvent from the air separating conduits by means of separators under pressure and providing one or more safety pressure regulators to control the pressure in the whole system.

l. In the method of recovering Montan wax by extracting brown coal with solvents in a hot state, the improvement which coinprises extracting the brown coal in a closed vessel under a total pressure exceeding one, but not exceeding 1.5 atmospheres produced by correspondingly increasing the temperature of the solvent.

2. In the method of recovering Montan wax by extracting brown coal with solvents in a hot state, the improvement which comprises extracting the brown coal as wet as it.

comes from the pit in a closed vessel under a total pressure exceeding one, but not exoeeding 1.5 atmospheres produced by correspondingly increasing the temperature of the solvent.

In testimony whereof we aiix our signatures.

ERICH ROECKNER. FRITZ ZSCHOCH. 

